It all changed after 1997, and now at least 1 HKPID parent (I.e the dad) must be resident in HK at the time of birth for overseas born children to qualify for ROA at birth.
My dad was born in HK. but I and my sisters were born in the UK. and we all have permanent residency.
I think it's different if you were born before 1997?, but DD was born in 2017 so we have to go through the 7 year residency requirement. Would be happy to be wrong (again) if there is a faster way.